Project Summary/Abstract HIV incidence rates during the postpartum period for South African women are among the highest in the world. Little is known, however, about the sexual behaviors that put women at risk of HIV infection postpartum and how these behaviors differ for younger and older women. Theoretical and empirical research on HIV risk outside of the postpartum period suggests relationship power is key to understanding risk, and that younger woman, and especially those with the fewest resources, may have less relationship power and greater risk due to their age. However, the role of relationship power in predicting women?s HIV risk during the postpartum period has not been studied. It is also unclear with regard to age whether it is women?s absolute age, where she is at in the life course (e.g., is she a first time parent), whether it is the age- disparity in her relationship, or whether it is age in conjunction with a lack of resources that influences her risk. Therefore, we propose new research to understand how age influences HIV risk (measured in this study through unsafe sexual behavior and STI incidence postpartum), and the extent to which the association between age and HIV risk may be explained by differences in relationship power among women with varying levels of resources. To test our hypotheses, we will conduct secondary data analysis with 945 HIV- women between the ages of 14-45 using SAHAPS data. SAHAPS was an intervention trial with 1,520 HIV+ and HIV- women designed to evaluate a model of psychosocial support. In SAHAPS, we assessed the efficacy of the intervention on STIs and inconsistent condom use postpartum but did not comprehensively describe sexual behavior or assess factors associated with HIV risk postpartum. Therefore, the specific aims of the proposed research are to (1a) Develop a classification system of women connected to developmental stage; (1b) Assess whether women?s age, developmental stage, and age relative to her partner (age-disparity) are each associated with STI incidence at 14 weeks postpartum and sexual behaviors at 14 weeks and 9 months postpartum; (2) Determine whether the association between age/developmental stage/age-disparity and STIs/sexual behavior is exacerbated for women with fewer resources and (3) Determine whether relationship power during pregnancy mediates the association between women?s age/developmental stage/age-disparity and STI incidence at 14 weeks postpartum and sexual behavior at 14 weeks postpartum and 9 months postpartum. The findings will help the Principal Investigator, an early stage investigator, move forward with her program of research to design developmentally appropriate interventions tailored to HIV- women seeking postpartum care.